avoid header naming collisions with Base64Transcoder.h

This change avoids header name collisions when a project contains another file
named Base64Transcoder.h (e.g., OAuthConsumer).
Merge pull request #174 from lionheart/master

avoid header naming collisions with Base64Transcoder.h
EM Customizations
Merge branch 'master' of https://github.com/uservoice/uservoice-ios-sdk